Multi-Body Analysis of Landing Phase of a Lunar Lander

The presented work of thesis has the main objective of describing the study of the landing stability of a lunar lander, accomplished through a multi-body dynamic analysis with Altair Hyperworks software package. This dissertation is the summary of a six-month work experience conducted at Thales Alenia Space Italia (TASI) in the headquarters of Turin, which is the prime contractor for the study of the European Large Logistic Lander (EL3), an independent vehicle designed for future international lunar exploration activities, envisioned as a versatile system that can support multiple and different types of mission. The landing of a vehicle on the surface of a planetary body is one of the greatest challenges in space exploration environment, since it is one of the most critical phases during a space mission. This scenario has been analysed thanks to a multi-body model of the lander created using Altair MotionView and solved by the solver, in order to simulate several critical landing configurations and to individuate the worst one in terms of stability. To achieve this task, a first Design Of Experiments (DOE) analysis using Altair HyperStudy has been implemented through a series of combinations of different input variables (i.e attitude and velocity of the lander, slope of the lunar surface, presence of an obstacle). This study has allowed to individuate critical landing scenarios in terms of stability, which have been analysed in detail introducing three important features in order to consider non-linearities of the phenomenon. Initially, a friction coefficient has been considered for interactions between footpads of the lander and lunar soil. Subsequently, a sensitivity analysis regarding shock absorbers, has allowed to study how the lander stability is influenced by a variation of their stiffness parameters. The shock absorber is a collapsible element assembled inside each leg of the lander, which has the function of absorbing the energy generated when the lander impact against lunar soil. Shock absorbers have been implemented inside the model, through a Python code. Finally, flexible bodies of lander’s leg have been created applying the theory of Component Mode Synthesis of Craig-Bampton.